A nunchaku-like nonlinear optical chromophore for improved temporal stability of guest-host electro-optic materials

Article abstract of DOI:10.1016/j.dyepig.2013.06.034

A novel nunchaku-like organic second order nonlinear optical chromophore containing a D-π-A backbone and a rigid biphenylene unit was prepared. The UV-vis absorption spectra studies demonstrated that the large rigid structure could suppress dipole-dipole interactions effectively. The electro-optic coefficient of a poled film containing 20% wt of the new dye doped in amorphous polycarbonate afforded a value of 39 pm/V at 1310 nm. Compared with results obtained from a similar D-π-A chromophore without the rigid isolated group, the new dye gave better performance. Moreover, the electro-optic film prepared with the new dye gave greater temporal stability, compared to a similar D-π-A doped poled film that was reported previously. These results indicated that the introduction of a biphenylene group could effectively reduce the intermolecular electrostatic interactions and aid the alignment of the chromophores.

Full text of DOI:10.1016/j.dyepig.2013.06.034

Accepted Manuscript
A Nunchaku-like Nonlinear Optical Chromophore for improved temporal stability of
Guest-Host Electro-Optic materials
Heyan Huang, Guowei Deng, Jialei Liu, Jieyun Wu, Peng Si, Huajun Xu, Shuhui Bo,
Ling Qiu, Zhen Zhen, Xinhou Liu
PII:
S0143-7208(13)00248-9
10.1016/j.dyepig.2013.06.034
DYPI 4005
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 22 April 2013
Revised Date: 27 June 2013
Accepted Date: 28 June 2013
Please cite this article as: Huang H, Deng G, Liu J, Wu J, Si P, Xu H, Bo S, Qiu L, Zhen Z, Liu X, A
Nunchaku-like Nonlinear Optical Chromophore for improved temporal stability of Guest-Host Electro-
Optic materials, Dyes and Pigments (2013), doi: 10.1016/j.dyepig.2013.06.034.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
1. A novel nunchaku-like organic second order NLO chromophore containing a D-π-A backbone
and a rigid biphenylene unit was prepared.
2. The chromophore demonstrates good thermal stability, solubility, weak intermolecular
interactions and a large electro-optic effect.
3. The influence of the rigid biphenylene group on the temporal stability of poled electro-optic
films was also investigated.

ACCEPTED MANUSCRIPT
A Nunchaku-like Nonlinear Optical Chromophore for improved
temporal stability of Guest-Host Electro-Optic materials
Heyan Huang ab, Guowei Deng ab, Jialei Liu a, Jieyun Wu ab, Peng Si ab, Huajun Xu ab
Shuhui Bo a, Ling Qiua, Zhen Zhen a, Xinhou Liu a*
,
a Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and
Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China
b University of Chinese Academy of Sciences, Beijing 100043, PR China
Abstract
A novel nunchaku-like organic second order nonlinear optical chromophore containing a D-π-A backbone and a
rigid biphenylene unit was prepared. The UV-vis absorption spectra studies demonstrated that the large rigid
structure could suppress dipole-dipole interactions effectively. The electro-optic coefficient of a poled film
containing 20% wt of the new dye doped in amorphous polycarbonate afforded a value of 39 pm/V at 1310 nm.
Compared with results obtained from a similar D-π-A chromophore without the rigid isolated group, the new dye
gave better performance. Moreover, the electro-optic film prepared with the new dye gave greater temporal
stability, compared to a similar D-π-A doped poled film that was reported previously. These results indicated that
the introduction of a biphenylene group could effectively reduce the intermolecular electrostatic interactions and
aid the alignment of the chromophores.
Keywords: nonlinear optical materials; chromophore; biphenylene; electro-optic; temporal stability; poled film
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1. Introduction
Organic electro-optic (EO) materials have drawn a great deal of attention in recent decades due to their
attractive potential applications in telecommunications such as phased array radar, optical gyroscopes and
modulators [1-6]. Organic and polymeric nonlinear optical (NLO) materials have many advantages over
conventional inorganic/semi-conductor EO materials, such as large nonlinear optical coefficient, ease of synthetic
design, simple preparation and low cost. To realize application of devices, organic EO materials are required to
fulfill several requirements: large optical nonlinearity, minimal optical loss at operation wavelength, good
mechanical strength and processability for multilayer fabrication, thermal stability in the device processing and
long-term stability of polar order [7]. The long-term temporal stability is the indispensable requirement for organic
EO materials, and also the challenge for the practical application.
Guest-host EO polymers are composite materials which contain nonlinear optical chromophores as a dissolved
guest and a polymer host. Such guest-host types were believed to be advantageous systems for the research of
structure-property relationships and prototype proof-of-concept EO devices due to their facile preparation [8].
However, for practical application, some problems such as macro-phase separation, lower loading density, should
be solved. More importantly, the thermal relaxation of the poling-induced order offered unsatisfactory temporal
stability. Although using high Tg polymers as the host could enhance the stability of guest-host materials to some
extent [8, 9], some excellent NLO chromophores could not tolerate the stringent condition of such high poling
temperatures. Several approaches, including the covalent incorporation of NLO chromophores into the structures
of main-chain polymers [10-13] and side-chain polymers [14, 15], the self-assembly or the layer-by-layer
deposition processes [16-18], and a variety of cross-linkable EO polymers [19-22], have been proposed to resolve
these problems. Nevertheless, these systems require more complex synthetic effort compared to simple guest-host
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polymers, although they could effectively address the stability issues of EO polymers.
Designing new chromophores which can reduce favorable intermolecular interactions has been proposed to be a
novel approach to improve the temporal stability of guest-host polymers [23-26]. The rigid rod-like structures of
biphenyl or biphenylene units potentially take preferential orientation induced by intermolecular interaction or an
external field [27-30]. If these units are introduced into the NLO chromophores, the temporal stability of the
poling-induced alignment of chromophores may be enhanced. The introduction of the biphenyl or biphenylene
units onto chromophore units has scarcely been investigated [31, 32] and no research on the influence of the units
on the temporal stability has been reported. In this article, a new molecular design route is reported to develop the
new nonlinear chromophore. Owing to the molecular shape, it is referred to as “nunchaku-like” molecule [29]. We
designed a new nunchaku-like NLO chromophore constructed by connecting a rigid biphenylene unit and a D-π-A
conjugated structure via a flexible spacer. The solubility of the chromophore will decrease due to the introduction
of a rigid biphenylene unit, conversely the flexible spacer can improve the solubility. The influence of the
biphenylene unit on the aggregation of chromophores was studied, guest-host EO polymers based on amorphous
polycarbonate (APC) and polymethylmethacrylate (PMMA) as the hosts were prepared. The EO activities of these
materials, especially the long-term temporal stability were investigated in detail.
2. Experimental
2.1 Materials and instrument
Biphenyl-4,4'-diol was purchased from Beijing Ouhe Technology Co.Ltd. All other solvents and chemicals were
purchased from Beijing Chemical Reagents Company. All the reagents were used as received unless otherwise
stated. Compound A was synthesized by our group, 4-((6-chlorohexyl)(methyl)amino)benzaldehyde and TCF
acceptor were prepared according to the literature [31, 33].
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1HNMR spectra were determined using a Varian Gemini (400 MHZ) NMR spectrometer (tetramethylsilane as
internal reference). The Mass spectra were obtained on MALDI-TOF (Matrix Assisted Laser Desorption/Ionization
of Flight) on BIFLEXIII(Broker Inc.) spectrometer. Elemental analyses were taken from a Thermo Finnigan Flash
EA1112 microelemental analyzer. The UV-vis spectra were performed on Hitachi U2001 photo spectrometer.
FT-IR spectra were recorded on BIO-RAD FTS-165 spectrometer. The melt points were obtained by TA DSC Q10
under N2 at a heating rate of 10 °C/min. The TGA was determined by TA TGA Q50 with a heating rate of 10 ℃/
min under the protection of nitrogen.
2.2 Syntheses
2.2.1 Synthesis of Compound 1
A diethyl ether solution (50 mL) of 4-((6-chlorohexyl)(methyl)amino)benzaldehyde (1.76 g, 4.0 mmol), NaH
(1.20 g, 50 mmol), and compound A (1.76 g, 4.0 mmol) was stirred at room temperature for 24 h, then poured into
ice water (200 mL). The mixture was extracted with dichloromethane (3×50 mL), and dried over magnesium
sulfate. The extract was concentrated by rotary evaporation, the resulting product was purified by silica-gel column
chromatography with a mixture of ethyl acetate and petroleum ether (v/v =1/9) as the eluent. The viscous
reddish-brown liquid was obtained (1.12 g, yield: 84%). IR(KBr), υmax/cm−1: 2932, 2858 (C−H), 1604, 1524
(benzene ring), 1274, 1184, 956, 818, 698. 1H NMR (400 MHz, Acetone) δ 7.46 (dd, J = 8.9 Hz,1.5Hz, 2H), 7.38
(d, J = 4.0 Hz, 1H),7.17 (dd, 1H), 6.95 (s, 2H), 6.74 (dd, J = 8.9 Hz, 1.5Hz, 2H), 6.49 (d, J = 4.0 Hz, 1H),3.60 (t, J
= 6.7 Hz, 2H), 3.42–3.36 (m, 2H), 2.97 (s, 3H), 1.83–1.74 (m, 2H), 1.62 (dt, J = 15.0, 7.5 Hz, 2H), 1.50 (dt, J =
14.3, 7.0 Hz, 2H), 1.43–1.35 (m, 2H). MS, m/z: 333.13(M+).
2.2.2 Synthesis of Compound 2
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A solution of compound 1 (1.00 g, 3.0 mmol) in anhydrous THF (10 mL) was prepared, purged with nitrogen,
and cooled to −78 °C. Then the solution was added dropwise n-BuLi (2.32 mL, 2.5 M in hexanes), and the
resulting mixture was stirred for 1 h. Anhydrous N,N-dimethylformamide (DMF) (0.28 mL) was added, and the
mixture was stirred for one additional hour. Saturated NH4Cl solution was added to quench the reaction, and the
mixture was then warmed to room temperature. The mixture was poured into water and the organic layer was
extracted with dichloromethane (3×50 mL). The combined organic layers were washed with water and dried over
anhydrous MgSO4.The extract was concentrated by rotary evaporation, the resulting product was purified by
silica-gel column chromatography with a mixture of ethyl acetate and petroleum ether (v/v =1/6) as the eluent.
Yield: red solid (0.98 g, 91%). m.p.: 64.54 °C. IR(KBr), υmax/cm−1: 2932, 2858 (C−H), 1658 (−CHO), 1597, 1516
(benzene ring), 1381, 1184, 1045, 956, 810. 1H NMR (400 MHz, Acetone) δ 9.86 (s, 1H), 7.82 (d, J = 4.0 Hz, 1H),
7.46 (d, J = 8.9 Hz, 2H), 7.22 (d, J = 4.0 Hz, 1H), 7.18 (s, 2H), 6.74 (d, J = 8.9 Hz, 2H), 3.60 (t, J = 6.7 Hz, 2H),
3.46 – 3.39 (m, 2H), 3.00 (s, 3H), 1.83 – 1.74 (m, 2H), 1.63 (dt, J = 15.0, 7.5 Hz, 2H), 1.50 (dt, J = 14.3, 7.0 Hz,
2H), 1.38 (dt, J = 7.3, 4.5 Hz, 2H). MS, m/z: 361.13(M+).
2.2.3 Synthesis of Compound 3
Biphenyl-4,4'-diol (0.66 g, 3.5 mmol) and compound 2 (1.27 g, 3.5 mmol) were added into a mixture of
anhydrous K2CO3(6.90 g, 50 mmol) and KI (0.913 g, 5 mmol) in anhydrous DMF (100 mL) with stirring. After
reaction at 80 °C for 12 h, the mixture was poured into an excess of NaOH aqueous solution (0.1 mol/ L) and was
extracted with dichloromethane (3×50 mL). The combined organic layers were washed with saturated salt water
and dried over anhydrous MgSO4. After removal of the solvent, the crude product was purified by silica-gel
column chromatography with a mixture of acetone and petroleum ether (v/v =1/3) as the eluent. Yield: orange-red
solid (0.93 g, 52%). m.p. (with decomposition): 201 °C . IR(KBr), υmax/cm−1: 3410 (Ph-OH), 2935, 2858 (C−H),
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1658 (−CHO), 1593, 1500 (benzene ring), 1250 (C−O−Ph), 1177, 1134, 1115, 821. 1H NMR (400 MHz, Acetone)
δ 9.85 (s, 1H), 8.31 (s, 1H), 7.80 (d, J = 4.0 Hz, 1H), 7.56–7.38 (m, 5H), 7.29–7.15 (m, 3H), 7.01–6.86 (m, 4H),
6.79–6.58 (m, 3H), 4.03 (t, J = 6.4 Hz, 2H), 3.44 (m, 2H), 3.00 (s, 3H), 1.86–1.75 (m, 2H), 1.66 (dt, J = 15.0, 7.5
Hz, 2H), 1.56 (dt, J = 14.4, 7.0 Hz, 2H), 1.46 (dd, J = 15.0, 8.1 Hz, 2H). MS, m/z: 511.68(M+).
2.2.4 Synthesis of Chromophore BPTCF2
TCF (0.29 g, 1.5 mmol) and compound 3 (0.25 g, 0.5 mmol) were dissolved in anhydrous methanol (30 mL)
under stirring. After heating under reflux for 4 h the mixture was concentrated by rotary evaporation, the crude
product was purified by silica-gel column chromatography with a mixture of ethyl acetate and petroleum ether (v/v
=1/2) as the eluent. Yield: green powder (0.25 g, 74%). m.p. : 137.41 °C. IR(KBr), υmax/cm−1: 2932, 2860 (C−H),
2226 (C≡N), 1593, 1523 (benzene ring), 1276 (C−O−Ph), 1049, 949. 1H NMR (400 MHz, Acetone) δ 8.29 (s, 1H),
8.13 (d, J = 4.0 Hz, 1H), 7.65 (d, J = 4.0 Hz, 1H), 7.52–7.39 (m, 5H), 7.24–7.16 (m, 3H), 6.95 (dd, J = 8.8
Hz,1.5Hz, 2H), 6.88 (dd, J = 8.6 Hz, 1.4Hz, 2H), 6.82 (s, 1H), 6.79–6.65 (m, 3H), 4.01 (t, J = 6.4 Hz, 2H),
3.50–3.41 (m, 2H), 3.03 (s, 3H), 1.85 (s, 6H), 1.79 (dd, J = 14.4, 6.8 Hz, 2H), 1.67 (dd, J = 14.5, 7.4 Hz, 2H),
1.60–1.51 (m, 2H), 1.50–1.40 (m, 2H). 13C NMR (101 MHz, Acetone) δ 177.60, 175.34, 159.32, 157.67, 154.69,
151.30, 140.94, 139.01, 135.35, 133.25, 129.95, 128.41, 124.68, 116.95, 116.72, 115.87, 113.41, 112.96, 99.18,
68.70, 52.97, 38.73, 27.68, 26.90, 26.51. MS, m/z: 692.53(M+). Anal. Calcd. for C43H40N4O3S: C,74.54; H, 5.82;
N, 8.09. Foud: C, 74.40; H, 5.86; N, 8.03.
2.3 Film preparation
For the UV–vis analysis and r33 measurements, guest–host polymers films were prepared by formulating
chromophore BPTCF2 into APC (Tg = 190 °C) and PMMA (Tg = 128 °C). The BPTCF2 (15 mg) were mixed
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with APC (75 mg) in dibromomethane(0.65 mL) as the solvent. After stirring for 12 h, the solutions were filtered
through a 0.22 ꢀm Teflon membrane filter and spin-coated onto indium tin oxide (ITO) glass substrates at room
temperature with the spinning rate of 700 rpm to give the films and then baked overnight at the room temperature
under vacuum, yielding optical quality thin films with thickness of around 3 ꢀm. The other films were obtained
using the same process. The poling process was carried out at a temperature of about 10°C above the Tg of the
polymers.
Scheme 1
3. Results and discussion
3.1 Synthesis and characterization
The synthetic route towards the nunchaku-like NLO chromophore BPTCF2 containing a rigid biphenylene unit
and the D-π-A conjugated structure is depicted in Scheme 1. Treatment of the 4-((6-chlorohexyl)(methyl)amino)
benzaldehyde with Wittig salt A and NaH afforded compound 1 in a reasonable yield, followed by a Vilsmeier
reaction to yield the corresponding aldehyde 2. Compound 3 was obtained through an SN2 reaction between
compound 2 and biphenyl-4,4'-diol. Finally the TCF acceptor unit was introduced into the chromophore using a
known condensation reaction [34-37]. The structure of BPTCF2 was confirmed by IR spectroscopic analysis,
1HNMR, 13CNMR , CHN elemental analyses and mass spectroscopy.
3.2 Thermal property of the chromophore
Chromophores must be thermally robust enough to withstand encountered temperatures in electric field poling
and subsequent processing of chromophore/polymer materials. The decomposition temperatures of the
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chromophore can be assessed by techniques such as thermal gravimetric analysis (TGA) and differential scanning
calorimetry (DSC). The thermal property of BPTCF2 was investigated by TA TGA Q50 under N2 at a heating rate
of 10 °C/min. BPTCF2 displayed high thermal stability with 5% loss temperature (Td) higher than 235 °C, which
was high enough for the application in EO device preparation [38].
3.3 UV-Vis spectra
It has been suggested that the solvatochromic effects are related with the molecular nonlinearity of NLO
chromophores [39-42]. In order to reveal the effect of electron donor with a rigid isolated group on the electronic
structures of dipolar chromophore BPTCF2, UV-vis absorption spectra were measured quantitatively in a series of
solvents with different polarity so that the solvatochromic behavior could be investigated. As shown in Fig. 1 a), in
non-polar solvents such as 1,4-dioxane and toluene, BPTCF2 exhibited a progressive red-shift of the maximum
absorption (λmax) and a saturation behavior was found in chloroform. With a further increase of solvent polarity, it
reversed to a hypsochromic shift in chloroform, dichloromethane (DCM), acetone and acetonitrile, namely
negative solvatochromism [41]. This interesting solvent-dependent spectral behavior suggested that the structure of
BPTCF2 can be easily influenced on the basis of the dipole formed by charge migration from the donor to the
acceptor in the most polar solvents. Notably, similar solvent-dependent changes of absorption spectra could also be
found for many merocyanine dyes. Therefore, the solvatochromism has been commonly regarded as an indication
of molecular nonlinearity of NLO chromophores [40].
Fig.1
The UV–vis spectra of BPTCF2 was also determined in chloroform with different concentrations (from 0.4×
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10-5 to 10×10-5mol·L-1), which was shown in Fig. 1 b). The shape of the absorption band has not changed
apparently as the concentration increased even the maximum concentration increased to 10-4 order of magnitude.
Inspection of Fig. 1 c) clearly shows the relationship of the concentration and absorbance. It was not difficult to
find that the absorbance was increasing linearly as the concentration increased, which showed that the interval of
absorbance change was highly uniform. These results indicated that there are only weak dipole-dipole interactions
among the chromophores. The strong dipole–dipole interaction could easily induce the aggregation of
chromophores, and even nano-crystal generation (self-assembly) via a solvent exchange method [40]. Unlike other
chromophores we studied, no crystallization behavior was observed for chromophore BPTCF2. These results
confirmed that the introduction of a rigid isolated group on electron donor could widen the distance between
chromophores and weaken the dipole–dipole interactions between dipolar molecules, which benefit the
macroscopic electro-optic efficiency.
3.4 Nonlinear optical property
In order to investigate the NLO property of chromophore BPTCF2, a guest-host EO polymer system was
explored. The poling process was carried out at a temperature of about 10°C above the Tg of the polymer. The EO
coefficients of the poled films were determined by the simple reflection technique initially proposed by Teng and
Man [43, 44]. The r33 values were calculated by the following equation:
3/2
3
λ
Ι
m
(n2 − sin2
n2 (n2 − 2sin2
θ
)
1
(1)
r33 =
4
π
V
m
I
c
θ
) sin2
θ
where r33 is the EO coefficient of the poled polymer, λ is the optical wavelength, h is the incidence angle, Ic is the
output beam intensity, Im is the amplitude of the modulation, Vm is the modulating voltage, and n is the refractive
indices of the polymer films.
The r33 values of poled APC/10%BPTCF2, APC/20%BPTCF2 and APC/30%BPTCF2 were 19 pm/V, 39
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pm/V, and 24 pm/V, respectively. The maximum r33 value of 39 pm/V was obtained when the loading density
reached 20%wt. This result is much better than that for DFTC-1 which was 30 pm/V [45]. The enhancement of the
EO activity further demonstrated that the rigid isolated group on electron donor effectively suppressed the
dipole-dipole interaction and assisted the orientation of chromophores during poling process.
Moreover, the order parameter changes of the poled EO films were studied through measuring the UV-Vis
absorption spectra of EO films before and after poling [46]. After the corona poling, the chromophores in the
polymer were aligned, and the absorption intensity decreased due to birefringence. From the absorption changes,
the order parameter (Φ) can be described according to the following equation: Φ = 1−A1/A0, where A0 and A1 are
the absorbance of the un-poled and poled EO polymer films at normal incidence. The Φ values of poled
APC/20%BPTCF2 film and PMMA/10%BPTCF2 film were about 27.7% and 23.9% (Fig. 2), which showed that
the Φ values had reached the average values and that the poling process was typically efficient. The Φ values are
related to the chromophores' orientation，and more effective chromophore orientation would provide larger Φ
values . The obtained higher Φ values indicated that BPTCF2 could effectively orientate in the poled films, which
was caused by the introduction of rigid isolated group.
Fig.2
3.5 The temporal stability
The long-term stability of the poled EO films was investigated. As shown in Fig. 3 a), after annealing at 85°C
for 500 h, the poled film of APC/20%BPTCF2 can retain more than 85% of its initial r33 value, and this
percentage was considerably higher than those of APC/10%DFTC-1 investigated previously, where only 75% of
the initial r33 value was kept after 300 h [47]. In the common guest-host organic EO materials, the Tg greatly
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influenced the temporal stability of the EO activity, and the EO material that has a higher Tg usually has a better
temporal stability [8]. In this work, the Tg of APC/20%BPTCF2 and the benchmark APC/10%DFTC-1were 141
°C and 150 °C, respectively, APC/20%BPTCF2 exhibited more promising long-term temporal alignment stability,
although it has the lower Tg. The improvement of temporal stability for APC/20%BPTCF2 provided direct
evidence that the relaxation of chromophores in the poled films had been restricted through introducing the
biphenylene unit. The improved temporal stability was probably contributed to by two aspects. On the one hand
there were the weak non-covalent interactions such as π-π stacking between chromophores (mainly biphenylene
groups) and polymer backbones (phenyl groups). On the other hand, due to the biphenylene units potentially
taking preferential orientation induced by intermolecular interaction, such kind of non-covalent interaction assisted
the alignment of chromophores during poling and restricted the movement of chromophores after poling.
To further investigate the influence of biphenylene unit on the temporal stability and determine which factors
play the major role. Two kinds of guest-host polymers using PMMA as host were investigated. Fig. 3 b) showed
the decay of the poled films of PMMA/10%BPTCF2 and PMMA/10%DFTC-1 at 55 °C. After a fast decay at the
initial 50 h, 74% of the initial r33 value was retained over 300 h for PMMA/10%/BPTCF2, the
PMMA/10%DFTC-1 decayed below 60% only after 150 h although both systems had a similar Tg.
PMMA/10%BPTCF2 also exhibited more promising long-term temporal alignment stability. These results
indicated that the main reason of the guest-host EO polymers containing chromophore BPTCF2 exhibited good
temporal stabilities was the weak intermolecular non-covalent interactions, it was also confirmed that the rigid
isolated group in electron donor enhanced the temporal stability of the guest-host EO material.
Fig.3
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4. Conclusion
In summary, a new NLO chromophore BPTCF2 with a large rigid isolated group was successfully synthesized and
characterized by 1HNMR, 13CNMR, CHN elemental analyses and MS. The intermolecular interactions and
molecular nonlinearity were studied by UV-vis absorption spectroscopy and these results confirmed that the
isolated group could greatly reduce intermolecular interactions. EO films were prepared by doping chromophore
BPTCF2 in APC or PMMA with different loading densities, and they showed high EO activity (39 pm/V).
Moreover, the temporal stability of poled APC/20%BPTCF2 film and PMMA/10%BPTCF2 film could retain
85% (500 h) and 74% (300 h) of the initial values at evaluated temperature (85 °C and 55 °C ) respectively, which
were much better than films prepared by traditional FTC chromophores.
Acknowledgments
We are grateful to the Directional Program of the Chinese Academy of Sciences (KJCX2.YW.H02), Innovation
Fund of Chinese Academy of Sciences (CXJJ-11-M035) and National Natural Science Foundation of China (No.
11104284 and No. 61101054) for the financial support.
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Figure Captions
Fig. 1 a) Solvatochromic behavior of BPTCF2 recorded in different solvents (2×10-5
M) of varying dielectric constants (1,4-dixoane:2.25; toluene: 2.38; chloroform: 4.81;
dichloromethane: 8.93; acetone:20.7; acetonitrile: 37.5). b) UV-vis absorption spectra
of BPTCF2 in chloroform with different concentrations. c) Linear plot of the
concentration and absorbance.
Fig. 2 UV-Vis absorption spectra of E-O polymers BPTCF2 doped in a) APC; b)
PMMA before and after poling.
Fig. 3 Temporal stabilities of the poled films. a) APC/20% BPTCF2 and APC/10%
DFTC-1. at 85oC. b) PMMA/20% BPTCF2 and PMMA/10% DFTC-1 at 55oC.
Scheme 1 Chemical structures and synthetic scheme for chromophore BPTCF2
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Fig. 1
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Fig. 2
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Fig.3
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Scheme 1
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